Submitted to: Foodborne Pathogens and Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/30/2010
Publication Date: 3/1/2011
Citation: Bhaduri, S., Chaney, K.J., Smith, J.L. 2011. A procedure for maintenance of the virulence plasmid (pYV) in Yersinia pestis under culture conditions. Foodborne Pathogens and Disease. 8:459-463. Interpretive Summary: Yersinia pestis, the causative agent of bubonic plague in humans, is also found in food and can cause a febrile illness in humans. Thus, food can have a significant role in the dissemination of human plague. There is a concern for risk assessors about the presence of Y. pestis in food. A virulence plasmid (pYV) of 70-kb is directly involved with virulence of this pathogen. The pYV is unstable in Y. pestis and the pathogen dissociates into avirulent clones (not lethal to mice; does not cause plague) after laboratory cultivation or during food processing. The loss of pYV leads to the loss of virulence and the eventual overgrowth by pYV less cells. Until now, there has been no method to determine the stability of pYV in Y. pestis. This problem was eliminated by developing a procedure to detect maintenance of pYV in Y. pestis during storage and laboratory manipulation. This technique should greatly assist both regulatory agencies and the food industry in detecting the presence of pYV in Y. pestis and in studying pYV-bearing Y. pestis since loss of the pYV during experimental procedures is prevented. Further, these techniques should also greatly assist medical and public health laboratories in identifying this pathogen.
Technical Abstract: The pathogenicity of Yersinia pestis depends on the presence of a virulence plasmid (pYV). The unstable nature of pYV in Y. pestis leads to the eventual outgrowth of pYV less cells due to its higher growth rate. Thus, it was necessary to develop procedures to monitor the presence of the plasmid during cultivation, storage, and laboratory manipulations. A procedure was developed to monitor the presence of pYV in Y. pestis by using low calcium response (Lcr) and Congo red (CR) binding techniques. The selection of pYV in the isolated clones was confirmed by PCR and by the expression of pYV-associated phenotypes. Thus, using this procedure, Lcr-CR positive clones can be isolated for use in the development of growth models of virulent Y. pestis in food.